Re: [Datadraw-user] BNF in 42

[Richard P. <rdp...@gm...>]

Your are far more experienced then me regarding complex language parsing.  I
take your words for granted blindly.

* I allow strings in the grammar rules to be lex-style regular
expressions.  What do you think?*

That is what I wished.  I was reading about LALR and it seems feasible.

Is your example part of the same syntax of defining relationship and classes
or a different syntax on a different file type?

The good point about the previous was cleanness based on indentation...
Although, I don't have anything wonderful to propose.

Regards

Richard


On Sun, Dec 28, 2008 at 5:41 AM, Bill Cox <bi...@bi...> wrote:

> Hi, Richard.
>
> I've written a ton of lex/yacc flex/bison based parsers.  Here's one
> thing I've found.  Most formats are context sensitive.  You just can't
> parse them the easy way, but have to build a parse tree and then
> traverse it manually to extract data.  Icky, but true.  This is
> massively true for VHDL, even thought the Preface of the VHDL Language
> Reference says it's not.  It's even true for Verilog.  Simple formats,
> like Synopsys Liberty format, are massively context dependent.
>
> In 42, I figured I'd give up on allowing generic code to execute for
> each matched rule, and just go ahead and build a parse tree for the
> user.  That separates all the application specific code from the grammar
> definition, and should help make the grammars more reusable and easier
> to read.
>
> I allow strings in the grammar rules to be lex-style regular
> expressions.  What do you think?
>
> The attached file is a grammar that I currently parse to build a parser
> rule database.  Then, I'm planning to write a BNF interpreter and
> re-parse this file using the rules defined in the file.  Once that
> works, I was planning to start writing the rest of the core 42 parser in
> 42 directly, and then start on the interpreter for it.  When the
> interpreter is running, I can start writing libraries to compile more
> advanced 42 constructs into simpler code which can be directly written
> out in C.  Anyway, that's the plan... too bad the holidays wont last
> forever - I'll probably have to get too focused on real work to make
> much progress come January.
>
> Regards,
> Bill
>
> Regards,
> Bill
>
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> Datadraw-user mailing list
> Dat...@li...
> https://lists.sourceforge.net/lists/listinfo/datadraw-user
>
>